RESUMO
Area V4 has numerous, topographically organized connections with multiple cortical areas, some of which are important for spatially organized visual processing, and others which seem important for spatial attention. Although the topographic organization of V4's connections with other cortical areas has been established, the detailed topography of its connections with subcortical areas is unclear. We therefore injected retrograde and anterograde tracers in different topographical regions of V4 in nine macaques to determine the organization of its subcortical connections. The injection sites included representations ranging from the fovea to far peripheral eccentricities in both the upper and lower visual fields. The topographically organized connections of V4 included bidirectional connections with four subdivisions of the pulvinar, two subdivisions of the claustrum, and the interlaminar portions of the lateral geniculate nucleus, and efferent projections to the superficial and intermediate layers of the superior colliculus, the thalamic reticular nucleus, and the caudate nucleus. All of these structures have a possible role in spatial attention. The nontopographic, or converging, connections included bidirectional connections with the lateral nucleus of the amygdala, afferent inputs from the dorsal raphe, median raphe, locus coeruleus, ventral tegmentum and nucleus basalis of Meynert, and efferent projections to the putamen. Any role of these structures in attention may be less spatially specific.
Assuntos
Córtex Visual/química , Córtex Visual/fisiologia , Vias Visuais/química , Vias Visuais/fisiologia , Tonsila do Cerebelo/química , Tonsila do Cerebelo/fisiologia , Animais , Atenção/fisiologia , Núcleo Caudado/química , Núcleo Caudado/fisiologia , Macaca , Macaca mulatta , Colículos Superiores/química , Colículos Superiores/fisiologiaRESUMO
Development is often described as temporal sequences of developmental stages (DSs). When tables of DS are defined exclusively in the time domain they cannot discriminate histogenetic differences between different positions along a spatial reference axis. We introduce a table of DSs for the developing chick optic tectum (OT) based on time- and space-dependent changes in quantitative morphometric parameters, qualitative histogenetic features and immunocytochemical pattern of several developmentally active molecules (Notch1, Hes5, NeuroD1, ß-III-Tubulin, synaptotagmin-I and neurofilament-M). Seven DSs and four transitional stages were defined from ED2 to ED12, when the basic OT cortical organization is established, along a spatial developmental gradient axis extending between a zone of maximal and a zone of minimal development. The table of DSs reveals that DSs do not only progress as a function of time but also display a spatially organized propagation along the developmental gradient axis. The complex and dynamic character of the OT development is documented by the fact that several DSs are simultaneously present at any ED or any embryonic stage. The table of DSs allows interpreting how developmental cell behaviors are temporally and spatially organized and explains how different DSs appear as a function of both time and space. The table of DSs provides a reference system to characterize the OT corticogenesis and to reliably compare observations made in different specimens.
Assuntos
Colículos Superiores/citologia , Colículos Superiores/embriologia , Animais , Embrião de Galinha , Imuno-Histoquímica , Neurônios/química , Neurônios/citologia , Colículos Superiores/químicaRESUMO
We analyzed the potential input and output components of nitric oxide synthase (NOS)-containing neurons in the rat superior colliculus (SC). To identify whether NOS-positive neurons receive glutamatergic input we investigated the colocalization of NOS with NMDA receptor subunit R1 (NMDAR1). In addition, to examine whether putative nitric oxide synthesizing neurons represent a neurochemically specific or distinct subpopulation of cells in the SC we studied the colocalization of NOS with the neurotransmitter GABA, the calcium-binding proteins parvalbumin, calbindin and calretinin and with neuropeptides such as somatostatin, substance P and neuropeptide Y. We found that 90% of NOS-positive neurons in the superficial layers of the rat SC express NMDAR1. Nearly 20% of the population of nitridergic neurons also expresses GABA and 15% of them express parvalbumin. NOS-positive neurons in the superior colliculus did not contain calretinin, calbindin or either of the neuropeptides tested. The results of this study show that the capacity for synthesizing NO in the SC is largely restricted to neurons that receive glutamatergic inputs and that some of these neurons express GABA or parvalbumin.
Assuntos
Neurônios/química , Óxido Nítrico Sintase/análise , Parvalbuminas/análise , Receptores de N-Metil-D-Aspartato/análise , Colículos Superiores/química , Vias Visuais/química , Ácido gama-Aminobutírico/análise , Animais , Calbindinas , Ácido Glutâmico/metabolismo , Imuno-Histoquímica , NADPH Desidrogenase/metabolismo , Neurônios/citologia , Neuropeptídeo Y/análise , Ratos , Proteína G de Ligação ao Cálcio S100/análise , Colículos Superiores/citologia , Vias Visuais/citologiaRESUMO
The distribution of mRNA transcripts corresponding to the alpha7 and alpha8 subunits of the nicotinic acetylcholine receptors (nAChRs) was studied in selected structures of the chick visual system with non-radioactive in situ hybridization and immunohistochemical techniques. The results indicated that the alpha7 and alpha8 nAChR transcripts are widely distributed in the brain, exhibiting differential expression in some structures but also some degree of co-localization. The pattern of localization of alpha7 and alpha8 nAChR transcripts was highly correlated with immunohistochemical data, with very few instances of possible mismatches between the distribution of mRNAs and their corresponding proteins.
Assuntos
Corpos Geniculados/química , Receptores Nicotínicos/análise , Receptores Nicotínicos/genética , Colículos Superiores/química , Animais , Galinhas , Fibras Colinérgicas/química , Fibras Colinérgicas/fisiologia , Expressão Gênica/fisiologia , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Técnicas Imunoenzimáticas , Hibridização In Situ/métodos , RNA Mensageiro/análise , Receptores Nicotínicos/imunologia , Colículos Superiores/citologia , Colículos Superiores/fisiologia , Receptor Nicotínico de Acetilcolina alfa7RESUMO
The ultra-structural development of synapses in retino-receptive layers of the opossum superior colliculus was studied by the ethanolic phosphotungstic acid (E-PTA) method. There was a tendency for a slight reduction in the diameter of synaptic disks, a rise and fall of numerical densities and, except for an ephemeral period, a general increase in the proportion of "frown" among curve synapses. The lack of strict synchrony and the occurrence of different patterns of changes suggest that multiple factors contribute to synaptic maturation.
Assuntos
Gambás/anatomia & histologia , Retina/ultraestrutura , Colículos Superiores/ultraestrutura , Sinapses/ultraestrutura , Vias Visuais/ultraestrutura , Animais , Axônios/ultraestrutura , Dendritos/ultraestrutura , Etanol , Imuno-Histoquímica , Gambás/metabolismo , Ácido Fosfotúngstico , Coloração e Rotulagem , Colículos Superiores/química , Colículos Superiores/crescimento & desenvolvimento , Sinapses/química , Vias Visuais/metabolismoRESUMO
Injections of a retrograde tracer into the accessory optic nucleus of the basal optic root (nBOR) of the pigeon, combined with 5-HT immunochemistry, revealed that serotonergic projections to the nBOR appeared to originate mainly from the median (MR) and paramedian (PMR) raphe nuclei. These projections were confirmed by the significant decrease in 5-HT immunoreactivity observed in nBOR after lesions in MR and PMR. These data characterize distinct sources of 5-HT innervation to the pigeon nBOR and suggest that those afferents could represent part of a modulatory system that contributes to the role of the nBOR in optokinetic mechanisms.
Assuntos
Nervo Óptico/química , Serotonina/análise , Colículos Superiores/citologia , Animais , Columbidae , Imuno-Histoquímica , Microinjeções , Microesferas , Neurônios/química , Rodaminas , Colículos Superiores/química , Vias VisuaisRESUMO
A small number of enkephalin-like immunoreactive cells were observed in the ganglion cell layer of the pigeon retina. Many of these neurons were identified as ganglion cells, since they were retrogradely labeled after injections of fluorescent latex microspheres in the contralateral optic tectum. These ganglion cells were mainly distributed in the inferior retina, and their soma sizes ranged from 12-26 microns in the largest axis. The enkephalin-containing ganglion cells appear to represent only a very small percentage of the ganglion cells projecting to the optic tectum (less than 0.1%). Two to 7 weeks after removal of the neural retina, there was an almost complete elimination of an enkephalin-like immunoreactive plexus in layer 3 of the contralateral, rostrodorsal optic tectum. These data provide evidence for the existence of a population of enkephalinergic retinal ganglion cells with projections to the optic tectum.